1. Field of the Invention
The present invention relates to a patch test material for the detection of metal allergies in dentistry, which is used to make simple and highly accurate determinations of whether or not metal allergies are developed in the presence of a dental metal (a pure metal or a metal alloy) to be topically applied with an allergic reaction aid.
2. Statement of the Prior Art
Metal allergies refer to an allergic phenomenon caused by a metal, which is an incomplete antigen (called hapten) that becomes an antigen only when the metal bonds to tissue proteins. In other words, upon directly contacting the skin, a certain metal has a primary influence upon the structure of a cell and the process of an enzymatic reaction, thus causing contact dermatitises. Included further in allergic diseases developed as antigen-antibody reactions are skin ulcers, stomatitis, conjunctivitis, sensitive pneumonia, bronchial asthma, pneumonic fibrosis and so on.
Metals included in dental metallic materials and responsible for metal allergies are not only base metal elements such as Be, Ni, Co, Fe and Cr but also noble metal elements such as Au, Pt, Ag, Cu and Hg. Referring in detail to the metal allergies as mentioned above, a metal is present in the form of three phases, i.e., a metallic vapor, a metal salt and a pure metal or a metal alloy.
Not only metal allergies but also cancers or acute toxicoses are caused by metallic vapors emanating from metal melts. It is also well-known that metal allergies due to salts of metals used in plating, coating and leather tanning fields such as, for instance, nickel, cobalt and chromium, appear as chronic dermatitises and asthmatic diseases.
Unlike a pure metal or a metal alloy, a metal salt undergoes easy ionization and becomes a metal hapten upon contacting the skin or the mucous membranes of the respiratory organs. The metal hapten then bonds especially to proteins in tissue fluids, giving an organometallic compound which in turn becomes an antigen so sensitive to an individual as to produce an antibody. If the antigen re-enters the individual, then metal allergic reactions appear as antigenantibody reactions. It is understood that metal allergies are developed through the following three barriers:
(1) A metal is ionized.
(2) Antigenicity cannot be acquired until the thus ionized metal bonds to a high molecule in tissue fluids and becomes an organometallic compound.
(3) An antigen-antibody reaction appears only after the antigen re-enters an individual.
Metal allergies cannot be fully developed until the above three barriers are passed through.
Heretofore, the development of contact dermatitises due to metal allergies as mentioned above has generally been examined by the following patch test. As an example, the determination of metal allergies due to Ni is made as follows:
Metallic Ni is dissolved in an electrolyte into NiSO.sub.4.6H.sub.2 O, which is then regulated to a concentration of 2.times.10.sup.-1 moles/liter with distilled water. The resulting solution is added dropwise onto gauze, which is afterwards applied thereon with a patch test plaster. After allowed to stand for 48 hours, the patch testing plaster is removed. After the lapse of further 24 hours, reaction sites are observed to estimate inflammations on them. The estimation of the reactions has been made in terms of the magnitude of positive reactions in comparison with controls comprising a plaster alone. To sum up, the reactions to metal allergies are generally examined by a method comprising the steps of, firstly, dissolving the metal for its ionization to form a metal salt solution; secondly, impregnating one or three droplets of that solution into gauze; and finally, applying a sealable patch test plaster thereon. In some cases, use may be made of first-aid plasters such as Kizu-Pad or a band aid (manufactured by Meisei Yakuhin Kogyo, K. K.). To examine metal allergic reactions on pure-metal elements used for dentistry, it is known to use such aqueous media of metal salts as set out in Table 1, given below.
TABLE 1 ______________________________________ No. Metal % Base ______________________________________ 1 CuSO.sub.4 5 Aq 2 CuSO.sub.4 2 Aq 3 K.sub.2 Cr.sub.2 O.sub.7 0.4 Aq 4 NiSO.sub.4 5 Aq 5 NiSO.sub.4 2 Aq 6 CoCl.sub.3 2 Aq 7 HgCl.sub.2 0.1 Aq 8 HgCl.sub.2 0.05 Aq 9 SnCl.sub.3 2 Aq 10 SnCl.sub.3 1 Aq 11 CdSO.sub.4 1 Aq 12 HAuCl.sub.4 0.2 Aq 13 H.sub.2 PtCl.sub.6 0.5 Aq 14 PdCl.sub.2 1 Aq 15 FeCl.sub.3 2 Aq 16 SbCl.sub.3 2 Pet. 17 AgBr 2 Pet. 18 ZnCl.sub.2 2 Pet. 19 MnCl.sub.2 2 Pet. ______________________________________
The aqueous media specified in Table 1 are all in the form of metal salts. The metal salts are placed on a pad in the form of one droplet, if liquefied, or a half grain of rice, if pasted, and the pad is applied on the back of a patient with the aid of Miniplaster (manufactured by Torii Yakuhin, K. K.).
In some cases, a dental Ni-Cr-Co alloy has been formed as such into a disc-like test piece of 4 mm in diameter and 1 mm in height, which has then been applied on a testing patch or a first-aid plaster to determine metal allergic reactions. However, this method is uncommon. That is, the function of the patch test plaster is only to apply a conventional test piece.
Heretofore, the metal allergic reactions have generally been examined by dissolving a metal for its ionization to form a metal salt solution and applying it onto gauze to make a determination of whether or not a living body becomes inflamed by allergic reactions.
However, the metals required for dental purposes are so particularly difficult to ionize that allergic reactions do not appear easily. With noble metals such as Au, Pt and others most commonly used as dental metals, such a tendency becomes especially marked. As an example, aqua regia or nitrohydrochloric acid capable of dissolving Au, Pt, etc. involves much difficulty in regulating it to around neutral pH of 7 to 8 due to its strong acidity. Results are also much different from those obtained with pure metals or metal alloys, once such dental metals are converted to their salts. In other words, the results often are useless, since the allergic reactions observed have taken place through the metal salts, not through the metals per se. Also, nonallergic inflammations due to pH values or salts are often mistaken for metal allergic inflammations. The dental metals are always used in the form of alloys except for rare occasions on which they are employed in their elemental state. Accordingly, it is likely that in the event that a certain pure metal, which is found to make no contribution to any allergic phenomenon, is alloyed with other metals, metal allergies may then be developed due to some synergistic effect resulting from such alloying.
The foregoing considerations imply that the examination of metal allergies by liquefying dental metals (alloys) into aqueous solutions of their salts tends to make erroneous judgements. In addition, the examination of allergic reactions on the individual metals isolated from an alloy is troublesome and, at the same time, is disadvantageous in that it is not possible to examine the metal allergic reaction of that alloy itself.
It is true that the method comprising forming a dental alloy itself into a disc-like test piece, by way of example, and applying it to the skin with the aid of a patch test plaster is simple to carry out, but it is difficult to ionize the alloy (or a metal) and convert it to a metal hapten by allowing it to contact the skin, unlike the metal salt, since it is through a complicated mechanism that the allergic reactions occur. Also, even though the metal hapten is formed, difficulty would be encountered in the event that it bonds especially to proteins in tissue fluids to form an organometallic compound which in turn becomes an antigen so sensitive to an individual as to produce an antibody. Especially, this holds for alloys of noble metals such as Au and Pt. Dentists should pay attention to the fact that in case a metallic prosthesis, especially if a metallic implant material is used without having a comprehensive understanding of the data of each patient about her or his metal allergies, the development of metal allergic reactions will bring results so harmful that inflammations, eruptions and erosions are spread to the mucous membranes i nthe mouth and, possibly, even to the whole system, thus resulting in chronic dermatitises which, reportedly, causes palmar and/or plantar pimples in particular. There is also the possibility that the bone may be absorbed or necrotized. It is thus essential and inevitable to make accurate determinations of the metal allergic reactions of a patch testing material for the purpose of preventing metallic allergies.